Conventional cable TV systems use hybrid fiber-coax networks (HFC). These HFC networks typically have a return path implemented in the RF domain and sometimes these HFC networks have certain digital conversions that don't change the nature of the system. These RF return paths transport RF signals from the subscriber to a data service hub. The data service hub can support video and data services for the subscriber. The upstream RF return transmissions from a subscriber of a network are important because they can support functions such as pay-per-view and video-on-demand from video set top terminals (STTs), referred to later as video services terminals (VSTS). Other functions for upstream RF return transmissions include security in cable TV digital rights management (DRM).
These functions usually require that the data service hub learn what programs the subscriber has viewed, so that the data service hub can automatically bill the subscriber and pay program suppliers. The upstream RF return transmissions from a subscriber of a data service hub can also be used for voice and data applications, both of which are two-way by nature. In conventional fiber-to-the-home (FTTH) systems in contrast with HFC systems, an RF return path from the subscriber's home back to the data service hub is usually not feasible because of the digital and packet-switching nature of the optical network.
In addition to this problem of supporting RF return paths in general, FTTH systems also face the problem of supporting RF return transmissions from modems that comply with certain cable modem standards, such as Data-Over-Cable Service Interface Specification (DOCSIS). DOCSIS is one set of conventional standards that define how almost all cable modems work. The standards are well-known to one of ordinary skill in the art. Some conventional solutions exist for supporting cable modem transmissions but these solutions often require modifications of the cable modems that are sold (or have been sold) to customers. Such solutions are costly and require subscribers to either purchase new equipment or modify existing equipment.
Conventional DOCSIS modems are available from a number of manufacturers who specialize in cable modems alone, so it would be impractical to make modifications to the way the DOCSIS modems work in order to service them in a FTTH system. Because of the predominance of DOCSIS in other parts of the world (such as EuroDOCSIS and eDOCSIS), and because of the trend to using DOCSIS in video services terminal communications in North America, there is a need in the art to transport upstream DOCSIS cable modem transmissions from a subscriber over an FTTH system. There is also a need in the art to modify one or more parts of the optical network in a FTTH system so that conventional DOCSIS modems being sold and that have been sold can be supported by the FTTH system.